Transmitter for telemetering systems



u y 2,` 1946. D. 'w. MOORE, JR

" TRANSMITTER FOR TELEMETERNG SYSTEMS INVENTOR DA o w MOORE Jr. BY 2 L E."

will* HNP ATTORNEY Patented July 2, 1946 TRANSMITTER FOR TELEMETERI G SYSTEMS David W. Moore, Jr., New York, N. Y., assig'nor to Fairchild Camera and Instrument Corporation,

a corporation of Delaware v y Application May 18, 1942, Serial No. 443,412l

'T 13 Claims. (Cl. 177-380) This invention relates to telemetering systems and magnetic iield responsive devices useful therein and, while it is of general application, it is particularly useful for giving remote indications of the readings of a plurality of aircraft instruments with the least possible modication of the instruments, per se.

While a wide variety of telemetering systems have heretofore been proposed for giving remote indications of the readings of meters, gauges, and other instruments, in "general these have required special construction of the meters or instruments or extensive modifications of existing devices to adapt them for use in the telemetering system. On the other hand, it is highly desirable to provide a telemetering system adapted to operate from standard meters and `instruments with a minimum of modification. This'is particularly true in the case of aircraft instruments, a very large number of which are generally included in an aircraft and in which the space and weight restrictions seriouslylimit the extent of permissible modification.

It is an object of the present invention, therefore, to provide a new and improved telemetering system for giving a remote indication of the readings of meters, gauges, and other instruments which involves a minimum modification of the instruments and is simple and reliable in con. struction and operation.

It is another object of the invention to provide` a new and improved magnetic eld responsive device which, While of 4general application, is particularly `suitable for use as a component element of the telemetering system of the invention. When so used, the only modiiication` kfor transmitting a periodicwave of a phase varying with the derived periodic wave.

of the meters, gauges, or other instruments is the attachment of a small permanent bar magnet to the indicating or metering element of the instrument.

In accordance with the invention, a sending station in a telemetering system comprises a primary metering element, a base-frequency-oscillator, a frequency multiplier vexcited from said oscillator, means for deriving from said multiplier a multiple-frequency wave varying in phase in accordance with the indication of the metering element, and means for transmitting a periodic wave of a phase varying with said derived periodic wave and a periodic wave of a. phase determined by theexcitation of said oscillator.

Also, in accordance with the invention,'a sending station in a telemetering system comprises a primary metering element, a periodic Wave supply circuit, means for producing a magnetic Also in accordance with a feature of the invention, the magnetic iield responsive device com; prises polyphase coil means, a pivoted supporting member for the coil means, and a, polyphase periodic wave supply circuit for exciting the `coil means to produce a rotating eld. The supporting member is balanced in the absence of an external magnetic eld but is subject to vibration in the presence of an external magnetic iieldhaving a component normal tothe pivotal axis of the coil meansand the phase of vibration of the supporting member varies in accordance with the direction of the magnetic field. The device also includes means responsive to the vibrationof the supporting member for giving an indication of the direction of such component of the external magnetic eld. y

For a better understanding of the present invention, together with other and vfurther objects thereof, reference is had tothe following description taken in connectionwith the accompanying drawing,l and its scope will be pointedY out in the appended claims.

Referring to the drawing, Eig. v1 is a circuit diagram, partiyfschematic,of a complete telemetering system embodying the invention and utilizing a magnetic eld responsive device and a phase-indicating device representing subsidiary features -of the invention; while Fig. 2 is adetailed View showing one relationship of the eldresponsive device of Fig. 1 to the meter being telemetered.

Referring nowto Figs.v 1 and 2 of the drawing, y, there is represented a telemetering system including a sending station I0 and a receivingstation Il, the sending station lkincluding a periodic wave supply circuit, such as the oscillator I2, generating a base frequency Fo. Coupled to the oscillator l2 are a plurality of frequency multipliers I3, I4 and I5 the output circuits of which comprise a plurality of periodicwave supply circuits of different but harmonically related frequencies,'each corresponding to one of the n 'ietering elements to be telemetered, and adapted to develop from the supply circuit vconsisting of the ling in phase in accordance with indications of a 's primary metering element I1 of [a meter `or inl ing the electrical oscillations generated by the strument Il, specifically in accordance ywith varif ations in the direction of a magnetic iield controlled by the primary metering;.-element. The

meter I l must of course bein 'close association 15 with the field-responsive device I9, one satisfac` tory relationship being shown' in Fig. 2 in which 1 the meter is immediately in front of the` device I6, corresponding elements of Figs. 1 and 2"being o identified by the same reference numerals. The

`iield responsive device IB-comprises a polyphase coil means, such Aas the two phase windings I9 and 29.23 disposed on a supporting member, such asthe cruciform magnetic armature or spider 2|,

of laminated or suitablydivided ymagnetic maf serial. As indicated, the armature is pivotedor otherwisefoscillatably mounted. ,In order to excite the two phase windings I9, I91and 2li, 20 'from the frequency multiplier |3, the1vvindingsl I9, vI9 -are connected tothe output circuit of this frequency multiplier through a phaseshifting conderiser2 22which 'co-operates ywith the output circuit of the frequency .multiplier I3 to provide a polyphaseperiodic wave supply 'circuit forV exciting thecoii means to produce a rotating iield. i The supporting member or amature 2| isnormally balanced labout itspivotal axis in the ab-r sence of an external magnetic neld, but is sub@ ject Iso-vibration in the presence of an external magnetic` field havinga componentin a plane normal to the pivotal axis of-the coil` means and its' supporting amature J 2|.; `Thereis therefore vprovided mean s for producing):l

magnetic kneld and means vfor varying the i direction oi'4 s'uch field fin accordance with the indication or the primary metering element. These means maytake the form of an angularly movable permanent magnet actuated by themetering element, for example, asmall permanent bar magnet` |1a attached `to the; primary metering element I1 pivotedor oscillatably mounted about. an axis parallel to that of the armature 2|. `This vibration of armature 2| about its pivot is due tothe magnetic couple between the rotatf `ing; iield of the coil means i9, i9 and 2li, 2l! and the component of the vmagnetic field of magnet |1a iria plane normal tothe pivotal vaxis ofi-.the coil' means. The magneticiield responsive device tion of 'the coil means and its supporting armarture 2| for giving an indication of the direction of the component of the magnetic field. This means comprises' a piezoelectric.r4 crystal 23j con nected by a link 24 to an extension'of'one vof the arms of the armature 2] forvibration thereby, the crystal 23 Vacting as a resilient restraining lmeans for limiting the amplitude vof vibration oi.'t thef-` supporting armature. `Preferably vthe armature 2| and its coilmeans I9, lil-.and `2\l,2Il and the resilient restraining means 723 have :a natural frequency of .mechanical vibration substantially the same as that of the polyphase vperi- 4 czzizrcuit of frequency multiplier I3 and condenser The crystal 23 constitutes means for developing from the mechanical vibrations of the armature 2| electrical oscillations varying in phase in accordance with the direction of the component of the magnetic field of magnet Ila. in a plane normal to.. the pivotal `axis of armature 2|, as explained hereinafter. The rest of the telemet'ering system comprises means for utilizquency multipliers. and I5 are magnetic iield responsive devices 26 and 21, respectively, indicated schematically since they may be in all respects similar to the device I6. Each of the elements 18,26, and 21 comprises means for deriving from its associated periodic wave supply circuit a periodic wave varying, in phase iny accordance vwith.indications of its associated primary metering elements l1, 28, and 29,*respectively. The output periodic waves of thennits i2, i 26, and 21 are applied'to means for transmitting these periodic waves comprising, a combining ampliiier 30, the output of which is `impressed upon an oscillator-modulator 3| coupled, in turn, to apower amplifier 32, the output circuit of which is coupled to a radiating antenna 33, these elementsy comprising means for transmitting the waves derived from the field responsive devices I6, 2S, and 21 and a periodic wave derived from the supply circuit comprising the youtput circuit ofroscillator I2. In the example described, each of these waves, as transmitted, is of the same phase andfrequency as theexcitation of its respective supplyfcircuit but, ofcourse, it will be understoodthat each wave may be stepped up or down in frequency for transmission, provided only that the transmitted wave is of a phase determined by or varying with the excitation of its respective source or supply'circuit.

The receiving station comprises means for receiving the transmitted periodic waves comprlsinga receiving antenna 34, an amplifier and detector 35and a plurality of filters 36, 31, 33,

uted winding 42,. energized from the received wave output of -fllter 31 through a phase-splitting `condenser 43 `and a movable element or armature 44 having a Winding 45 disposed thereon. 'The phase-responsive device 40 also includes a polyphase phase-'responsive means, such as the two-phase induction motor 46 having a iirst 'phase winding41 excited from the movable gwinding ofthe phaseshifting transformer 4| anda second phase winding 48 excited from another received wave of the same frequency as theoutput of the filter 31. This other received wave isyderived from a frequency multiplier 49 which'develops a frequency F1 from the periodic wave of base frequency Fn selected by the filter 39. The phase-responsive device 40 thus comprises means `responsiveto the phase relation between the excitation of the supply circuit constituting the output circuit of frequency multiodio wave supply circuit comprising the output 76 plier I 3 and the oscillations derived by eld re- The phase-responsive -and phase-k indicating device 40, per se, forms the subject matter of my copending divisional application,

Serial No. 477,757, filed March 2, 1943.

The receiving station II includes a plurality of other phase-responsive units- 53 and 5.4 energized from the variable phasevperiodic waves selected by the filters 38 and 33, respectively, and from periodic waves derived from the constant phase received wave selected by filter 36 through frequencyrnultipliers 55 and 56, respectively, for der-- veloping periodic waves of. frequencies F2 and Fa,

respectively. The frequency multipliers 49, y55 andl 56 thus comprise means for deriving fromthe;

received wave of the same frequency and phase as the output of oscillator `I2 va plurality of sec-V ondary Waves of the same harmonically rrelated frequencies F1, F2, and Fi as those derived by the frequencymultipliers I3,` I4 andy I5 at the .send-f ing station I0.

In considering the operation of the above-described telemetering system, it will be assumed thatv the oscillator I2 at the sending station I0.-

is generating a base frequency F which is utilized to excite the frequency multipliers I3, I4, and I5 for `developing high-frequency periodic waves, the frequencies Fo, Fi, F2, and Fzall being harmonically related. The periodic wave of frequency F1 is applied through the phase-splitting condenser v22 to the polyphase coil means I9, I8

and 20, 2l)v of the magnetic eld responsive. device I6 which excites its pivotedmagnetic armatu-re 2l. with a rotating magnetic'fleld.

balanced about its pivotal axis.Y However,fin

the presence of a magnetic field having a com-t ponent in a plane normal to the pivotalaxls of the armature 2| and its associated coil means, the magnetic couple between therotating field of the' armature 2| and the external field reverses the polarity during each cycle of rotation of the magnetic field, causing a vibration of the armaturev 2l and associated coil means at. the frequency of excitation. This mechanical. vibration is transmittedto, but restrained in ampli tude by, the piezoelectric crystal 23. which gen-- erates electrical oscillations of the same frequency and phase as the mechanical vibrations of armature 2|. In this case the external magnetic field is that developed by the permanent magnet I1a attached to the primary. metering' element I1. The phase of the mechanical vibra-V tions relative to the phase of the periodic wave supplied byv frequency multiplier JI3, andV thus the phase of the electrical oscillations developed by crystal 23, varies directly in accordance with the direction of the magnetic field of the magnet I1a and thus directly with the angular position of the primary metering element I1.

In a similar fashion, the magneticseld responsive devices 26 and 21 deriveperiodic waves of frequencies F2 and Fa from the periodic wave outputs of the frequency multipliers I4 and I5,

respectively, the derived periodic .wavesl varying in phase in accordance with the angular positions of the primary metering elements 28 and In the. absence of an external field, the armature 2l is' 29, respectively.v The output oscillations of the units I6, 26, and 21 can be utilizedsdirectly for givingindications of the directions of the magnetic fields corresponding thereto. In the present telemeteringsystem, they are combined with the output of theoscillator I2 inthe combining amplifier 30,;impressed on a carrier. wave in the` oscillator-modulator 3|, amplified in apower amplifierg32, and radiated by the antenna 33 for transmission. u

At the receiving station II, t he. transmitted carrier wave is picked up bythe antenna 34, amplified and detected in the u nit 35, and the mod- .ulationcomponents of frequenciesFo, F1, F2, and F3 selectedrby the filters 36, 31, 38, and 39, respectively. It will be appreciated, however, that, if desired, the periodic waves of frequencies Fo, F1, F2, and F3 may be transmitted by wire directly fromthe sending station I D to the `receiving station Il without the use of a radio link.

-Thevvariable phase periodic wave of frequency F1 selected by filter 31, is .applied through the phase-splitting lcondenser 43 to thel stationary arma-ture of thephase-shifting transformer 4I,

V the output of which is taken from the, movable Winding 45 and has a phase dependent upon the position of the movable element. The outputv of the winding 45 .is applied tov excite a first phase winding' 41 o f the two-phase phase-responsive induction motor 46, the second phase winding- 48 of which is excited with aperiodic wave, also of frequency Faderived bythe frequency multi-` plier ,49-4 which, .in,turn, is excited withthe received constant phase periodic wave of frequency g Fn selected by filter 36.

Itis .evident ,that the phase of, the periodic wave of frequency F1 selected byfllter 31 correspondsin phase with that developed by the mag-- netic field responsive device I6 at the sending stationand thus varies in .accordance with the angularpositionof the primary metering element 4.1. It .'isyalso evident that the. periodic wave of .frequency Frderived' from the frequency multiplier 49 through the filter 36 is of a constant y phase, Ibeing derived directly vfrom the .base-frequency oscillator ,.I, 2. Therefore, the relative phasesof these two periodicwaves is an indication of the angular position of the primary metering element.|1. -While therelative phases of t thesev twogwavesmay belmeasured by any suitable phase-responsive means, a preferred form is that comprising the phase-shifting transformer 4l landtvvo-phase induction motor46.

Assuming an, initial deflection o f the primary metering element I1 and a-zero reading of` the secondary metering element 5I, the output of the phase-shifting transformer 4I is not in phase withthat derived from the frequency multiplier 49,` thetwo phase windings 41 and 48 are. excited out of phase,and the motor 46 operates to adjust themovable winding 45A to such a position that these Atwo periodic Waves have the same phase,fwhen'the motor 46 is'rebalanced. At the same time, the secondary metering element 5I is actuated by the shaft v50 of the motor'46 and is movedthrough an angle equal tothe angle of deflection of the primary metering element I1.

' In a similarmanner the phase-responsive devices 53 and 54'andtheir associated filters 38 and 39, respectively, and frequency multipliers 55 and 56, respectively, operate to adjust the secondary metering elements 51 and 58, respectively, to correspond to the 4.positions of the primary metering elements v28, and l29,- respectively. While there has beenA illustrated.; by way of example, a system 7 y employing three primaryv metering elements an a like number oi' secondary metering'rele'ments, it will be understood that any desired number of metering elements may be included in the sending and receiving stations. It will also be understood that, instead of continuously transmitting periodic waves of different frequencies corre-` sponding tothe indications of the severalpri--y mary metering elementsftheseindications mayI be transmitted successively on a single wave .ofV

a single frequency by 'providing synchronousiy controlled selectors' at the-sending-andvnreceiving 4 Y stations.

The telemeteringsystem described has a num i ber of advantages. It requires no modification of the primary meters or instruments other than the attachment of a small permanent bar magnet to the metering element of eacii; if: providescon-I tinuous and' direct readings; it is substantiallyy insensitive to variations in the supply voltage vork frequency; and it requires a minimum frequency are sufiiciently slow that each wave is essentially a single constant frequency.

The field responsive devices I6, 26, 21 also have a number-oi advantages, per se;` they are direct reading and do not need to be re-oriented or re-adjusted to the null point for each reading; when amplitude as well as phase of the output of the device is compared with'that of the supply circuit, the device also gives anl indication of the' density of the component oitheexternal magnetic eld in a plane normal to the pivotal axis of the device, A

While there has `been described what is at present considered to be the preferred embodiment of this invention, it-will be obvious to those skilled in the art that `various changes and'modifications may be made therein without departing from the inventiornand it is, therefore. aimed in the appended claims to cover alllsuch changes and modifications asfall within the true spirit and scope of the invention l What is claimed is:

1. In a telemetering system, a sending.y station comprising a primary metering element, a. periodic wave-supply circuit, means for producing a` magnetic field, means for varying the direction of said field in accordance with the indication of said element, a magnetic field-responsive device for deriving from said supply circuit a periodic wavel Vband `for transmission `since the variations phase oi the waves of frequencies F1, F2, andFsf varying in phase in accordance with the direction oi' said field, and means for transmitting a periodic wave of a phase varying with said derived periodic wave. f i A 2. In a telemetering system,a sending station comprising a primary metering element, a. periodic wave supply circuit, an angularly movable permanent magnet actuated bysaid metering element. a magnetic field-responsive device for deriving from said supply circuit a, periodic wave varying in phase in'accordancewith` the direction of the field of said magnet, and means ior trans-A a periodic wave of a phase varying with said derived period wave.

4. In. a telemetering system, a sending station including a plurality of primary meteringelements, a plurality of periodic wave supply circuits of different frequencies each corresponding to one of said metering elements, meansfor producing `a plurality of magnetic fields, means for individually varying the directions of said fields in accordance with the indications of said metering elements, a magnetic eld-responsive device associated With each of said circuits for deriving therefrom a periodic wave varying in phase in accordance with the direction of its corresponding magnetic iield, and means for transmitting periodic waves of phases individually varying with said rderived periodic waves.

5. In a telemetering system, a sending station including a plurality of primary metering elements, a plurality of circuits for developing from said supply circuit a plurality of waves of harmonically related frequencies each corresponding to one of said metering elements, means for producing a plurality of magnetic elds, means for individually varying the directions of said fields in accordance with the indications of said metering elements, a magnetic field-responsive device associated with each of said circuits for deriving therefrom a periodic wave varying in phase in accordance with the direction of its corresponding magnetic eld, and means for transmitting periodic waves of phases individually varying with said derived periodic waves.

6. In a telemetering system, a sending station comprising a primary metering element, a polyphase periodic wave supply circuit, means for producing a magnetic field, means for varying the direction of said field in accordance with the indication of said element, a magnetic eld-responsive device disposed in said magnetic eld and consisting of polyphase coil means excited from said supply circuit, an oscillatable supporting member for said coil means, said supporting member being balanced` inthe absence of an external magnetic ileld but subject to vibration in the presence of said magnetic eld, the phase oi' said vibration varying in accordance with thev direction of said magnetic eld, means responsive to said vibration for developing a periodic wave varying in phase in accordance with the direction of said magnetic field, and means for transmitting a wave varying in phase with said developed periodic wave.

7. In a telemetering system, a sending station comprising a, primary metering element, a basei'requency oscillator, a frequency multipliexcited from said oscillator, means for deriving from said multiplier a multiple-frequency wave, means for producing a magnetic field, means for varying the direction of said field in accordance ing, polyphase coil means, an oscillatable sup- 1 porting member for said coil means, a polyphase periodic wave supply circuit for exciting said coil means to produce a rotating field, said supporting member being balanced in the absence of an external magnetic eld but subject to vibration in the presence of an external field having a corn ponent in a plane normal to the axis 'of oscillation of said coil means, the phase of said vibration varying in accordance with the direction of said magnetic field, and means responsive to said vibration for developing an electrical effect representative of the direction of said component of said external field.

9. A magnetic field responsive device comprising, polyphase coil means, an oscillatable magnetic armature for said coil means, a polyphase periodic Wave supply circuit for exciting said coil means to produce a rotating field, said armature being balanced in the absence of an external magnetic field but subject to vibration in the presence of an external field having a component in a plane normal to the pivotal axis of said coil means, the phase of said vibration varying in accordance with the direction of said magnetic field, and means responsive to said vibration for of an external magnetic field but subject to' vibration in the presence of an external field having a component in a plane normal to the axis of oscillation of said. coil means, the phase of said vibration varying in accordance with the direction of ysaid magnetic field, resilient revstraining means for limiting th`e amplitude of vibration of said supporting member, and means responsive to said vibration for developing an electrical effect representative of the direction of said component of said external field. y

11. A magnetic eld responsive device comprising, polyphase coil means, an oscillatable 'supporting member for said coil means, a polyphase periodic Wave supply circuit for exciting said coil means to produce a rotating field, said supporting member being balanced in the absence of an external magnetic field but subject to l0 vibration in the presence of an external field having a component in a plane normal to the axis of oscillation of said coil means, the phase of said vibration varying in accordance with the direction of said magnetic field, resilient restraining means for limiting the amplitude of vibration of said supporting member, said armature and said resilient means having a natural frequency of mechanical vibration substantially equal to'that of said periodic wave circuit, and means responsive to said` vibration for developing an electrical Aeffect representative of the direction of said developing from mechanical vibrations of said supporting member oscillations varying in phase in accordance with the direction of said component of said external field.

13. A magnetic field responsive device comprising, polyphase coil means, an oscillatable supporting member for said coil means, a polyphase periodic wave supply circuit for exciting said coil means to produce a rotating field, said supporting member being balanced in the absence of an external magnetic field but subject to vibration in the presence of an external field having a component in a plane normal to the axis of oscillation of said coil means, the phase of said vibration varying in accordance with the direction of said magnetic field, a piezoelectricdevice connected to said supporting member for vibration thereby and including means for developing an electrical effect representative of the direction of said component of said external field.

. DAVID W. MOORE. JR. 

